Their explanation about solving the inconsistency between the chrome browser logged in user and the google web site logged in users makes some amount of sense.

Their explanation about solving the inconsistency between the chrome browser logged in user and the google web site logged in users makes some amount of sense. I am sure there have been some interesting incidents where people's browsing habits were exposed to other users unintentionally and it's reasonable for Google to want to respond to that. It seems unnecessary however to auto-log in a person to the chrome browser when there is no such login in the first place to solve this though. It would make more sense to just display a warning when the state is inconsistent rather than start auto-logging people in (regardless of sync state).